
Working with disk images
You can use Disk Utility to create a "disk image." A disk image is a file that contains other files and folders. You can create a disk image using an existing disk, volume, or folder. You can also create blank disk images that you can add files and folders to later.
When you create a disk image you can erase it and change its volume format so that other computers, such as MS-DOS for Windows computers or UNIX file system computers, can read it.
You can use a disk image to move files from one computer to another, send them to other people in email, or burn the image on a CD or DVD disc as a backup copy. Disk images are also a convenient way to back up and restore your system software and files.
In the Finder, a disk image looks like a file with the extension ".dmg" (for example, Installer.dmg).
To access the contents of a disk image, you must open it. If you open a disk image that is encrypted, you must enter the password for it.
When you double-click a disk image file, the image is "attached" to Mac OS X and any volumes on it are "mounted," or opened. Icons for each volume in the disk image appear in the sidebar of Finder windows. To see the contents of the disk image, click the icon of a volume.
Once the volume is open, you can copy files and folders from it to your hard disk. If you created a blank disk image, you may be able to copy files from your hard disk to the image. You can also open files from the disk image. If the image format is "read/write," you can make changes to the files.